1. Field of the Invention
The present invention relates to an image forming apparatus in which an image corresponding to image data is reproduced by scanning an image carrier with a laser beam, and more particularly to an image forming apparatus in which the strength of a frame for accommodating and holding components constituting the image forming apparatus is enhanced.
2. Description of the Related Art
In an image forming apparatus employing the electrophotographic technique, a photoconductor which serves as an image carrier is uniformly charged, and then illuminated with a light image corresponding to image data, thereby forming an electrostatic latent image on the surface of the photoconductor. As a method for forming such a light image, a method is used in vogue in which the surface of the photoconductor is scanned in the direction of the rotation axis with a modulated laser beam emitted from a semiconductor laser that is driven and controlled in accordance with image data, via an optical system in which various optical components such as reflection mirrors, a lens, and a deflection mirror (polygon mirror) are held at predetermined intervals.
Such an image forming apparatus which uses a laser scanning device having an optical scanning system including a semiconductor laser, and in which the above-described electrophotographic technique is employed so as to reproduce an image in accordance with image data has been commercialized as a printer, a digital copier, a facsimile apparatus, or the like. In such an image forming apparatus, components including an expendable item are unitized into a single assembly, and the unit assembly is configured so as to be replaced with a new one by the user, thereby allowing the user to easily perform maintenance. This can save service expenses for replacing the assembly, and hence the total cost can be reduced.
In order to reduce the market price, the cost reduction has been performed in various points. With respect to the cost of components of an apparatus, for example, the price is reduced by, for example, reconsidering the components, reducing the number of components, and improving the productivity.
The components may be reduced in number and shared so as to realize the cost reduction. In this case, the apparatus must be designed in consideration of the strength and rigidity of the apparatus body. In the case where members for supporting a laser scanning device are used also for another purpose or reduced in number, for example, the supporting structure must be considered so as not to exert an adverse effect on the laser beam scanning. When the strength and rigidity of a frame structure for supporting a laser scanning device are reduced, vibrations due to the recording operation of the electrophotographic process section or the like adversely affects the laser beam scanning to cause shake, distortion, or the like to largely disturb an reproduced image, with the result that the image quality is greatly affected.
In a recent image forming apparatus, as describe above, various expendable items are enabled to be replaced in the form of a unit with new ones. In order to facilitate the replacement, therefore, an opening for operation must be formed in a frame which serves as a supporting structure of the apparatus body. When such an opening is formed, the strength and rigidity of the frame which serves as a supporting structure are weakened, and hence the frame for supporting the laser scanning device is caused to distort or shake by vibrations due to the recording operation or the like as described above, whereby the image quality is impaired.
Japanese Unexamined Patent Publication JP-A 11-95149 (1999) discloses a configuration in which a laser scanning device is attached to a frame of the body of an image forming apparatus via an additional reinforcing member, so that effects of shake and distortion due to vibration or the like created by the laser scanning device are eliminated to prevent the laser beam scanning from being disturbed. As the reinforcing member, a member formed by a rigid material such as iron is prepared. The laser scanning device is supported by the reinforcing member, and the reinforcing member is attached and fixed to the body frame, thereby preventing vibrations, distortion, and the like of the image forming apparatus body from being transmitted to the laser scanning device. As a result, the laser beam scanning can be stabilized, and the image quality is prevented from being lowered.
In the conventional art described above, the frame body which serves per se as a supporting structure of the body of the image forming apparatus is provided with strength and rigidity, so as not to transmit vibrations created by the image forming apparatus to the laser scanning device, whereby the occurrence of shake of the optical system or disturbance of the scanning operation is prevented. In the case where the body frame itself is problematic in strength, however, there is a fear that the laser beam scanning is largely disturbed even when a reinforcing member is directly attached to the laser scanning device itself.
In order to enable the user to easily perform maintenance, particularly, several partial openings must be formed in the frame structure so as to attach and detach replacement units for various expendable items, with the result that the strength and rigidity of the frame are reduced. Accordingly in order to enhance the strength of the frame, it is necessary to increase the thickness of each member constituting the frame structure or increase the diameter of a post(s) or the like.
However, such a configuration causes increases in weight and size of the whole apparatus and accordingly causes an increase in production cost.
In view of the problems discussed above, it is an object of the invention to provide an image forming apparatus in which the strength and rigidity of a frame structure for supporting a laser scanning device are enhanced, so that, when the laser scanning device is supported by the structure, disturbance of a scanning laser beam due to vibrations created by the image forming apparatus or the like is avoided, so as to prevent the image quality from being lowered.
It is another object of the invention to provide an image forming apparatus in which, even in the case where components constituting the image forming apparatus are to be easily replaced with new ones, the strength and the like of a frame structure can be sufficiently ensured, and also positional relationships between the frame structure and a laser scanning device can be satisfactorily ensured.
In order to achieve the objects, the invention provides an image forming apparatus comprising an image carrier which is optically scanned with a laser beam that is modulated in accordance with image data, for reproducing an image corresponding to the image data thereon; a laser scanning device having optical components, for scanning with the laser beam; a frame structure for supporting the image carrier and the laser scanning device, and a first reinforcing member attached to a portion where the frame structure is reinforceable in strength, for supporting the laser scanning device.
According to the invention, the configuration of the image forming apparatus makes it possible that the laser scanning device for scanning the surface of the image carrier with a laser beam in the main scanning direction is supported by the first reinforcing member which is disposed with the objective of reinforcing the frame structure that ensures a space for accommodating and holding components constituting the image forming apparatus. Therefore, it is not required to specially provide the laser scanning device with a reinforcing member for preventing shake and distortion of the laser beam due to vibrations of an image forming operation, so as to support the laser scanning device. In other words, the laser scanning device is fixed to and supported by the first reinforcing member which is previously disposed in order to reinforce the frame structure. The configuration can be simplified, and shake of the laser beam and the like can be effectively prevented.
According to the image forming apparatus of the invention, the frame structure is configured so that, when the image carrier is exposure scanned with the laser beam emitted from the laser scanning device, shake and distortion of the laser beam are prevented from occurring, and the laser scanning device is attached to the reinforcing member which is disposed with the objective of reinforcing the frame structure, thereby preventing the above-mentioned shake and distortion of the laser beam from occurring.
In the invention it is preferable that a part of the laser scanning device serves as the first reinforcing member.
According to the invention, since the first reinforcing member which constitute a part of the laser scanning device is attached to the frame structure to reinforce the frame structure, it is not required to specially provide the laser scanning device with a reinforcing member for preventing shake and distortion of the laser beam due to vibrations of an image forming operation, so as to support the laser scanning device. In other words, the frame structure is reinforced by the laser scanning device, with the result that the configuration can be simplified and shake of the laser beam and the like can be effectively prevented.
In the invention it is preferable that the laser scanning device is held by a first supporting member in which one face is opened so that predetermined mutual positional relationships among the optical components constituting the laser scanning device are maintained, and the first supporting member is fixed so that the opened face is opposed to the first reinforcing member.
According to the invention, the optical components can be easily integrated into the apparatus, and as well the first reinforcing member prevents dust from entering the first supporting member because it is fixed to the reinforcing member, whereby the optical components are prevented from being contaminated to cause the image quality to be impaired. Since the reinforcing member plays a role of a cover, it is not required to separately dispose a specific cover on the first supporting member
In the invention it is preferable that the frame structure has a basic configuration in which front and rear frames each configured by combining a plurality of rod-like members are coupled with each other by rod-like members to ensure a space which can accommodate components of the image forming apparatus, and the reinforcing member is disposed between the front and rear frames.
According to the invention, the reinforcing effect of the frame structure can be enhanced.
Since the frame structure is configured by combining the rod-like members and the frame structure is reinforced by the reinforcing member, furthermore, the opening which enables the image carrier or the like to be easily replaced with a new one can be easily formed, and the strength and rigidity of the frame structure can be sufficiently ensured by thereinforcing member.
As a result, the above-mentioned positional relationships between the laser scanning device and the image carrier are prevented from being broken.
In the invention it is preferable that a second reinforcing member is further disposed in a same manner as that of the first reinforcing member, and a second supporting member for supporting the image carrier is disposed on the second reinforcing member.
According to the invention, the strength and rigidity of the frame structure of the basic configuration can be further enhanced. When, in the frame, the second supporting member is disposed on the second reinforcing member, positional relationships between the laser scanning device and the image carrier can be held constant. During a process of scanning with the laser beam in the main scanning direction, therefore, positional relationships with respect to the image carrier are held constant with the result that an image formed by excellent scanning can be obtained.
Since the second reinforcing member for reinforcing the frame structure is disposed while ensuring positional relationships with the reinforcing member (first reinforcing member) to which the laser scanning device is attached and the image carrier is supported by the second reinforcing member, moreover, predetermined positional relationships between the two components can be maintained, and images can be stably reproduced without reduction in image quality.
In the invention it is preferable that a guiding portion for guiding the second supporting member which supports the image carrier is disposed in the second reinforcing member, a guided portion which is guided by the guiding portion is disposed in the second supporting member, and the second supporting member is detachable and attachable.
According to the invention, even in the configuration in which the image carrier is attached and detached in this way, the laser scanning device and the second supporting member are respectively supported by the first and second reinforcing members, and hence relationships between the two components are always held constant, so that satisfactory image formation can be performed.
In order to enable the image carrier to be attachable and detachable, an opening must be formed in the frame structure. Since the frame structure is configured by combining rod-like members as described above, such an opening can be easily ensured. Even when such an opening is formed, furthermore, strength and rigidity can be sufficiently ensured because the strength and rigidity of the frame structure including the first reinforcing member or the second reinforcing member are sufficiently ensured.
In the invention it is preferable that the second reinforcing member is fixed to the first reinforcing member so that a face of the first reinforcing member corresponding to a laser beam scanning direction is fixed to a face of the second reinforcing member corresponding to the laser beam scanning direction.
According to the invention, positional misalignment in a scanning direction (main scanning direction) along which the surface of the image carrier is scanned with the laser beam is eliminated, and constant relationships are maintained, whereby a more excellent image can be formed. Particularly the positional relationships in the main scanning direction can be sufficiently ensured by the first and second reinforcing members.